Infrared flare having a shroud for enhancing the radiation thereof



Jul 8, 1969 w. LA. 3,453,958

INFRARED FLARE HAVING A SHROUD FOR ENHANCING THE RADIATION THEREOF Filed Feb. 20, 1968 8 an? \r A inmwe'rs' United States Patent 3,453,958 INFRARED FLARE HAVING A SHROUD FOR EN- HANCING THE RADIATION THEREOF William Lai, 465 W. Portola Ave., Los Altos, Calif. 94022 Filed Feb. 20, 1968, Ser. No. 706,977 Int. Cl. C06d 1/10 US. Cl. 102-37.8 4 Claims ABSTRACT OF THE DISCLOSURE An infrared flare having a shroud mounted on the rear portion of the flare for enhancing the radiation of the flame emanating from the flare.

Background of the invention This invention relates generally to infrared flares and, more particularly, to a shroud for enhancing the radiation of the flare.

There has been a recent tendency to supplement radar detection and guidance systems with infrared or IR systems. Sources of radiation in the infrared spectrum are useful as target devices in testing equipment and training personnel in weapons having infrared sensitive homing mechanisms.

For the purpose of training personnel and development of new equipment, infrared flares, which can simulate the IR output from various thermal engines, are required. The infrared flares may be attached to the wings of target drones which are remotely controlled, or the flare may be propelled by rocket to high altitudes and suspended at the peak of its ascent by parachute. The flare may be ballon-dropped from aircraft or carried by a manned plane to train detection equipment operators.

The intensity and spectral characteristics of presentday flares are extremely sensitive to altitude since their operation depends upon afterburning with ambient oxygen. At extremely high altitudes the rarified conditions produce a shortage in the supply of oxygen necessary for the afterburning of the flare flame.

Summary of the invention The instant invention reduces the altitude sensitivity of the present-day flare by mounting a shroud around the rear of the flare thus making available a larger supply of oxygen for afterburning of the combustible products remaining in flare flame.

The present invention utilizes a hybrid-type flare of the type disclosed in my copending application entitled An Impingement and Composition Enhanced Infrared Flare, Ser. No. 704,739 filed Feb. 12, 1968, and therefore has the characteristics of restartability and throttleability. It should be realized, however, that the instant invention is not limited in its use to the hybrid-type flare but may be readily adapted for use with any conventional flare.

The high temperature combustion products generated in the mixer-nozzle section of the flare flow out of an annular nozzle in the form of an exhaust flame. The forward motion of the flare r'ams air through the inlet of the shroud. In this manner, the rarified conditions of high altitude are overcome and a larger supply of oxygen is made available for afterburning of the combustible products remaining in the flare flame.

It is therefore an object of this invention to provide an infrared flare having a shroud thereon for enhancing the radiation of the flare.

It is a further object of this invention to provide an infrared flare having a shroud thereon which is removable.

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It is still a further object of this invention to provide an infrared flare having a shroud thereon which is of light weight.

It is another object of this invention to provide an infrared flare having a shroud thereon which is economical to produce and which utilizes conventional, currently available components that lend themselves to standard mass production manufacturing techniques.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Description of the drawing The figure of the drawing represents a fragmentary side elevational view of the infrared flare and shroud of this invention.

Description of the preferred embodiment Referring now to the figure, the infrared flare 10 may be any conventional flare or more specifically of the type more fully described in my copending application entitled An Impingement and Composition Enhanced Flare, Ser. No. 704,739 filed Feb. 12, 1968, having oxidizer section 12, mixer-nozzle section 14 and nozzle 16. In accordance with the instant invention a pair of annular stepped rings 18 and 20 are mounted in any conventional manner, such as by welding on the exterior of the mixer-nozzle section 14 of the flare 10. Ring 18 is located at the midportion of flare 10, while ring 20 is located at the rear of the flare adjacent nozzle 16. If desired, however, the annular stepped rings 18 and 20 and the mixer-nozzle section 14 may be of one piece. A plurality of threaded studs 22 protrude from the rings 18 and 20. A shroud 24 fits onto step 26 on annular ring 18 and step 28 on annular ring 30. The shroud 24 is constructed in an annular configuration and of any suitable light-weight material, such as aluminum. More specifically, the shroud 24 is in the form of a pair of conical sections joined together at a point 25, intermediate the ends 31 and 33 with the diameter of the intermediate point 25 being less than the diameter of the ends 31 and 33. A pair of annular mounts 30 and 32 are secured to end 31 and to the central portion 25, respectively, by any suitable fastening means, such as welding. However, if desired, the entire shroud 24 including mounts 30 and 32, may be manufactured from one piece of material. For optimum results, length L for the shoud extending from the central portion 25 to the end 33 should be approximately equal to the diameter D of the opening of the nozzle 16 of the flare 10. The mounts 30 and 32 have a plurality of slots therein in line with the threaded studs 22 on the rings 18 and 20, or alternatively, if bolts are used in place of studs 22 holes may replace the slots. The shroud 24 is secured to rings 18 and 20 by any suitable fastening means, such as nuts 23, although it should be realized that the shroud 24 and the mixer-nozzle section 14 may be of a single piece of material. The type of mounting arrangement shown in the drawing permits the shroud 24 to be easily removed from the flare 10 and mounted on another similar type flare.

Mode of operation The radiant energy of the flame 36 exiting from nozzle 16 is greatly enhanced by the larger supply of oxygen made available by the shroud 24.

In accordance with the instant invention the flare 10 is towed behind a suitable aircraft or the like. Thus, at rarified conditions the forward motion of the flare 10 rams air through the inlet of the shroud (shown by arrows), thus introducing a larger supply of oxygen to the flame 36 for afterburning.

I claim:

1. An infrared flare comprising an annular nozzle at the rear portion thereof, a pair of annular stepped rings, one of said rings fixedly secured at the midportion of said flare, the other of said rings fixedly secured to the rear portion of said flare adjacent said nozzle, an annular shroud mounted adjacent the rear portion of said flare, said shroud being in the form of a pair of conical sections joined together at a point intermediate their forward and rearward ends, the diameter of said intermediate point being less than the diameter of said ends and a pair of annular mounts secured to the forward end and central portion of said shroud, respectively, fixedly securing said shroud to said annular rings of said flare, whereby the forward motion of said flare rams air through the forward end of said shroud thereby introducing a larger supply of oxygen to the flame emanating from the nozzle of said flare.

2. An infrared flare as defined in claim 1 wherein the distance from said intermediate point of said shroud to said rearward end being approximately equal to the diameter of the nozzle of said flare.

References Cited UNITED STATES PATENTS 3,051,085 8/ 1962 Finkelstein 10237.8 3,173,249 3/1965 Wiggins 60-245 3,221,497 12/1965 Forbes 60251 3,299,639 1/ 1967 Lagelbauer 60226 OTHER REFERENCES Dietz, Aviation Research & Development Handbook, 1958-1959, p. D-5 to D7.

SAMUEL FEINBERG, Primary Examiner.

J. FOX, Assistant Examiner. 

